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Diversity is Key to Stability

I was asked to speak to a Friendship Force group with guests from several countries around the world last week at McFarland Park. The topic I was asked to address was nature and its relationship to agriculture. Several college courses could be built around that broad topic, but I had about 30 minutes to touch on some basic ideas. McFarland Park was a good place to meet, too, with its varied native plant communities resting in the middle of America’s agricultural heartland.

You see, the agricultural Iowa we know today couldn’t exist had it not been for the highly diverse plant communities that covered the land for thousands of years prior to settlement by pioneering farmers. I was reminded of how important Iowa’s prairie heritage was as we walked along the Touch-a-Life paved trail between a reconstructed prairie and the little lake with its late summer algae blooms, fed by fertility lost from surrounding cropland. The group had been exposed to our endless fields of corn and soybeans for most of a week, but were being exposed for the first time to the foundation of that agricultural richness. Only prairie grasslands are capable of producing the kind of soil we so often take for granted. Woodlands can’t do it at all and wetlands produce soils that are rich enough, but often remain difficult to farm even with artificial drainage.

What made the prairies so unique, you may ask? In a word, it was their diversity. Our tall-grass prairies were composed of hundreds of species of plants. Some thrived best on well-drained to dry soils, while others could thrive in moist to totally saturated conditions. Yet others thrived best in between. Cold, hot, wet, or dry; something was always thriving and growing on the prairies.

Many legumes - plants that could capture atmospheric nitrogen and store it in plant-usable form in their roots - also grew on the prairie. This unique capability benefited not only the legumes, but all the plants that grew around them. Fertility was held in both living plant tissue and in humus, the centuries-long accumulation of organic matter in the soil. Erosion and nutrient loss was nearly impossible in the deep living fabric of tangled roots that bound the prairie ecosystem together.

Other players helped to maintain the prairie’s incredible diversity. They included large grazers like bison and elk that kept tall grasses from overpowering shorter-lived flowering plants. Although most prairie plants are perennials, there is a strong component of annual and biennial plants in a healthy and diverse native prairie. They depended on disturbances caused by animals as large as bison, as small as meadow mice and even mound-building ants. Erratic climate shifts are nothing new to the prairie midlands. Dry spells brought fires, and that, too, contributed to the diversity of plant communities that lived here. Take away any of these formative forces and the prairie would not have been what it was. Nor would the bountiful soils that support our agricultural economy have been what they were when we broke them for tillage.

We now live in a world that strives not for diversity, but for monocultures of single crop species. This is true in our lawns (including mine), as well as our crop fields. Even lumber production on national forest land focuses on even-aged planted stands of single species of trees that make eventual harvest easier and more efficient. Even-aged monocultures are the exact opposite of what nature has, and always will, try to create. We therefore shoulder a great deal of expense in our efforts to keep unwanted plants and animals from our managed stands of single target species.

There are lessons to be learned from nature. We’ll never see the prairies of old with their hundreds of species, but we can still benefit from natural services in erosion control, pollution control, fertility development, pest management and more when we strive to enhance diversity on the land. We improve our own ecological, agricultural and even financial stability when we diversify.